Three-dimensional printing systems and methods

ABSTRACT

This disclosure provides various systems and methods for three-dimensional printing in which data describing an object as a plurality of voxels is transferred as a print material to form the three-dimensional object independent of locking. That is, various systems and methods are provided herein in which the three-dimensional printing step is to transfer data representing various voxels into a corresponding physical object via a three-dimensional printer. The first step is repeated until all of the voxels are printed without waiting for any of the voxels of print material to lock. Accordingly, the three-dimensional printer can be used to print at least one subsequent object while the first object finishes locking.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C 119 to U.S. PatentApplication No. 62/468,931 filed Mar. 8, 2017 titled “3-DimensionalPrinting Systems and Methods,” which is hereby incorporated by referencein its entirety, including the appendix thereto.

TECHNICAL FIELD

This disclosure generally relates to three-dimensional printing systemsand methods. More specifically, this disclosure relates tothree-dimensional printing systems in which printing successive layersis not limited by locking delays.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the disclosure aredescribed herein, including various embodiments of the disclosure withreference to the figures listed below.

FIG. 1A illustrates a data transfer system for selectively printingvoxels of concrete and depositing fill material, according to oneembodiment.

FIG. 1B illustrates a cross section of the data transfer system of FIG.1A in which voxels of fill material have been deposited and voxels ofconcrete have been extruded.

FIG. 1C illustrates a perspective view of the data transfer system ofFIG. 1A for extruding concrete and depositing fill material in athree-dimensional array of voxels, according to one embodiment.

FIG. 1D illustrates a bottom view of the data transfer system in FIG. 1Awith selectively openable tubes for extruding concrete and depositingfill material, according to one embodiment.

FIG. 2A illustrates a two-dimensional array of injector printheads forinjecting a resin hardener into a container of resin, according to oneembodiment.

FIG. 2B illustrates a two-dimensional array of injector printheads beingretracted from a container of resin as they deposit resin hardener,according to one embodiment.

FIG. 3A illustrates a two-dimensional cross section showing an array ofneedle injector printheads inserted within a container, according to oneembodiment.

FIG. 3B illustrates the two-dimensional cross section of the containerin FIG. 3A with fill material inserted within the container around theneedle injector printheads.

FIG. 3C illustrates the two-dimensional cross section of the containerin FIG. 3A with the needle injector printheads partially retractedhaving selectively injected a bonding agent, according to oneembodiment.

FIG. 4A illustrates a focused beam for hardening a voxel within acontainer of a fill material, according to one embodiment.

FIG. 4B illustrates the focused beam of FIG. 4A having hardened fivevoxels within the fill material, according to one embodiment.

FIG. 4C illustrates the focused beam of FIG. 4A having hardened asequence of voxels to form a three-dimensional pattern.

FIG. 5 illustrates a simplified flow chart of a method of printing,according to one embodiment.

FIG. 6 illustrates a simplified flow chart of a method of printing threeobjects with parallel locking, according to one embodiment.

FIG. 7 illustrates an example of a computer system with various modulesfor controlling three-dimensional printing, according to one embodiment.

DETAILED DESCRIPTION

Many three-dimensional printing systems and methods forthree-dimensional printing utilize a multi-step process that includesprinting a flowable material and waiting for that flowable material to“lock” before more flowable material is added to the existing flowablematerial. For example, a printing system may print with a print mediasuch as polylactic acid (PLA), acrylonitrile butadiene styrene (ABS),acrylic, resin, etc. by printing a first, lowest layer and then, oncethe media has locked (e.g., hardened or cooled sufficiently to support asubsequent layer), printing a second layer. In many embodiments, asingle print head is used and the mechanical movement is generally slowenough that by the time the printer begins printing the second layer,the first layer has already locked.

If, however, an object resembling a pencil were printed standing on itsend, it is easily appreciated that the lower layers would need tosufficiently harden to support the top layers. A relatively fast printermay need to intentionally delay subsequent layers to ensure that theunderlying layers have locked. Some three-dimensional printers haveattempted to solve this problem by using cooling fluids or quick-lockingmaterial to decrease the lock time. As used herein, the term “locked”refers to any solidification process of a flowable material inthree-dimensional printing. Examples of locking include, but are notlimited to, cooling, hardening, drying, curing, phase-changing,undergoing a catalytic homopolymerization, undergoing a chemicalreaction, and the like.

An example of a print material with a relatively long locking time isconcrete. Current concrete three-dimensional printing may take multiplehours or days to print successive layers. Some approaches to decreasethe locking time include quick-curing concrete, sprays to decreaselocking time, and additives to decrease locking time. Even with theseimprovements, three-dimensional printing of large objects, such asstructures (e.g., houses, buildings, sculptures, etc.), can take hours,days, or even weeks to complete. Many components of a concrete structuremay require manual intervention using current approaches. For example,current processes for printing doorways, windows, overhangs, arches,etc. may require manual installation of concrete forms.

As described above, many existing systems and methods explicitly (orimplicitly by the inherently slow printing system) follow a process inwhich a first step is to transform data for a first layer of athree-dimensional object into a physical object via a three-dimensionalprinter. The second step is to wait for previous layer to lock beforebeginning the second layer. In some systems, the second step isinherently introduced based on the (slow) speed of the system. In othersystems, the second step may be explicitly introduced based on anexpected or average locking time of the material being printed. Thosetwo steps are repeated multiple times until each layer or voxel of thethree-dimensional object is printed. In such embodiments, thethree-dimensional printer is in use for the cumulative time it takes toprint each of the layers and for all of the layers to lock.

This disclosure provides various systems and methods forthree-dimensional printing in which data describing an object as aplurality of voxels is transferred to a three-dimensional objectindependent of locking. That is, various systems and methods areprovided herein in which a first step is to transfer data representingvarious voxels into a corresponding physical object via athree-dimensional printer. The first step is repeated until all of thevoxels are printed. The three-dimensional printer is then done and canbe used to print a second object or another, different object. Thesecond, locking step occurs independent of the three-dimensional printerand does not delay the transfer of data into a physical object.

As an example, a single three-dimensional printer may serially printmultiple objects. The last of the multiple objects may be printed beforethe first of the objects is fully locked. In such an embodiment, all ofthe multiple objects may lock in parallel. This may be especiallybeneficial when printing with materials that take a long time to lock.As used herein, a “layer” may represent, for example, a planar layerthat is one “voxel” thick. A voxel may correspond to the smallestfeature size achievable by a particular three-dimensional printer. Insome embodiments, the transfer of data representing an object to anactual object may include a conversion of the data to a plurality ofvoxels having dimensions corresponding to the resolution or minimumfeature size of a particular printing device or print media.

The specific systems and methods described below effectively separateprinting or data transfer stage from the locking stage. Printing speeds,or at least overall throughput of printing multiple objects, can begreatly increased by eliminating the need to wait for each subsequentobject to be fully locked. With the locking step removed from thethree-dimensional printing process, the number of printheads or nozzlescan be increased to further reduce the total print time.

A first stage of three-dimensional printing can be characterized as datatransfer. Data representing a physical, three-dimensional shape istransferred into a physical three-dimensional object via athree-dimensional printer. The data is effectively encoded in one ormore materials as a printed volume. In some examples, the printed volumemay be extruded, printed layer by layer, printed voxel by voxel, orotherwise transferred into a three-dimensional volume. In someembodiments, the printing process may include adding a material to anexisting material, hardening or curing specific voxels of an existingmaterial, or displacing one material with another material. In someembodiments, voxels of one or more types of materials may be added to avolume within a vacuum (e.g., within a vacuum chamber or in space).

In some embodiments, support material may reduce or eliminate post-printdeformation until the material is fully locked. In some embodiments,predictable deformation is used as part of the printing process. As anexample, an array (two-dimensional or three-dimensional) of printnozzles (more generally, “printheads”) may inject a print material intoa volume containing support material. The nozzles may, for example, beretracted from a bottom level of the support material up and out of thesupport material. As the nozzles are withdrawn, print material isinjected into the support material to displace the support material atspecific voxel locations. The support material substantially preventsthe print material from deforming as it locks. The nozzles may beinserted within another volume of support material for a subsequentprint operation while the first printed object is locking.

As a specific example, the support material may comprise a resin withina container. The two- or three-dimensional array of injector printheadsmay inject a resin hardener at specific locations within the containerof resin as the array of injector printheads is withdrawn from thecontainer. The entire printing process or “data transfer” may becompleted within a few seconds in many embodiments. That is, all of thevoxels of resin hardener may be deposited within the container of resinwithin a few seconds. The locking process may include the resin andresin hardener reacting to form hardened resin in, or approximatelywithin, the voxel locations at which the injector printheads injectedthe resin hardener. In some embodiments, the locking process may takeseveral minutes or even hours. However, the multi-dimensional array ofinjector printheads may be inserted within another container of resinfor data transfer of another three-dimensional object while the firstobject is locking.

Conventional three-dimensional printing may follow a pattern of: (i)print first layer, (ii) lock first layer, (iii) print second layer, (iv)lock second layer, (v) print third layer . . . , etc. In an embodimentin which it takes 5 seconds to print a layer and 15 minutes for thelayer to lock, the conventional approach could print two objects with 20layers in about 10 hours. In contrast, the multi-dimensional array ofinjector printheads that allows for parallel locking could print 180objects within the 10 hours and have another 180 that are in variousstages of locking.

In other embodiments, as further described below, a print material(e.g., concrete) may be extruded into a space and a fill material (e.g.,beads or gravel) may be selectively deposited to provide support for theprint material. In such an embodiment, a finished print may include acontained volume of voxels occupied by either print material or fillmaterial. Once the print material fully locks, the boundaries of thevolume may be released and the fill material may be removed to revealthe fully locked print material.

In another embodiment, a supercooled liquid may remain dormant untilnucleation points are created through focused ultrasound. Eachnucleation point may represent a voxel of the final printed object. Inanother embodiment, pellets of a plastic may have a solvent sprayed onthem at specific places as they flow into a container. In anotherembodiment, powdered metals may be bound with flux and soldered. Inanother embodiment, sand may be melted with beamformed radiation atvarious locations within a container.

Data transfer to a physical object can occur in a wide variety of othermanners. Additional examples include forming shape crystals by injectingchemicals, aiming electron or proton beams, focusing ultrasound, firinghigh velocity seed crystals into place, laser heating, etc. In each ofthese embodiments, shape data is transferred into a physical object veryquickly, but the material changes that take place (the locking) mayoccur over a longer time period.

As previously described, the locking stage may take some amount of timethat is significantly greater than the printing stage. Three-dimensionalprinting speeds are greatly increased by constructing the printingsystem in such a way as to allow for a printing method that separatesthe print and locking stages. Each of the various embodiments describedherein are merely examples of possible systems that allow for printingprocesses that are locking independent.

Some of the infrastructure that can be used with embodiments disclosedherein is already available, such as: general-purpose computers,computer programming tools and techniques, digital storage media, andcommunications networks. A computer may include a processor, such as amicroprocessor, microcontroller, logic circuitry, or the like. Theprocessor may include a special-purpose processing device, such as anASIC, a PAL, a PLA, a PLD, a CPLD, a Field Programmable Gate Array(FPGA), or other customized or programmable device. The computer mayalso include a computer-readable storage device, such as non-volatilememory, static RAM, dynamic RAM, ROM, CD-ROM, disk, tape, magneticmemory, optical memory, flash memory, or other computer-readable storagemedium.

Suitable networks for configuration and/or use, as described herein,include any of a wide variety of network infrastructures. Specifically,a network may incorporate landlines, wireless communication, opticalconnections, various modulators, demodulators, small form-factorpluggable (SFP) transceivers, routers, hubs, switches, and/or othernetworking equipment.

The network may include communications or networking software, such assoftware available from Novell, Microsoft, Artisoft, and other vendors,and may operate using TCP/IP, SPX, IPX, SONET, and other protocols overtwisted pair, coaxial, or optical fiber cables, telephone lines,satellites, microwave relays, modulated AC power lines, physical mediatransfer, wireless radio links, and/or other data transmission “wires.”The network may encompass smaller networks and/or be connectable toother networks through a gateway or similar mechanism.

Aspects of certain embodiments described herein may be implemented assoftware modules or components. As used herein, a software module orcomponent may include any type of computer instruction orcomputer-executable code located within or on a computer-readablestorage medium, such as a non-transitory computer-readable medium. Asoftware module may, for instance, comprise one or more physical orlogical blocks of computer instructions, which may be organized as aroutine, program, object, component, data structure, etc., that performone or more tasks or implement particular data types, algorithms, and/ormethods.

A particular software module may comprise disparate instructions storedin different locations of a computer-readable storage medium, whichtogether implement the described functionality of the module. Indeed, amodule may comprise a single instruction or many instructions, and maybe distributed over several different code segments, among differentprograms, and across several computer-readable storage media. Someembodiments may be practiced in a distributed computing environmentwhere tasks are performed by a remote processing device linked through acommunications network. In a distributed computing environment, softwaremodules may be located in local and/or remote computer-readable storagemedia. In addition, data being tied or rendered together in a databaserecord may be resident in the same computer-readable storage medium, oracross several computer-readable storage media, and may be linkedtogether in fields of a record in a database across a network.

Some of the embodiments of the disclosure can be understood by referenceto the drawings, wherein like parts are designated by like numeralsthroughout. The components of the disclosed embodiments, as generallydescribed and illustrated in the figures herein, could be arranged anddesigned in a wide variety of different configurations. Further, thoseof skill in the art will recognize that one or more of the specificdetails may be omitted, or other methods, components, or materials maybe used. In some cases, operations are not shown or described in detail.Thus, the following detailed description of the embodiments of thesystems and methods of the disclosure is not intended to limit the scopeof the disclosure, as claimed, but is merely representative of possibleembodiments.

FIG. 1A illustrates a data transfer system 100 for selectively printingvoxels of concrete and depositing fill material, according to oneembodiment. The illustrated data transfer system, or three-dimensionalprinter, 100 includes a control and supply component 105. The controland supply component 105 may control the extrusion and deposition ofprint material and fill material via concrete extrusion tubes 120 (shownwith light shading) and fill material deposition tubes 110 (shown withdark shading).

Concrete may be selectively extruded via the concrete extrusion tubes120 within divided sections or cells of a concrete printing printhead(e.g., cut-away section 151). Fill material, such as beads, plasticpellets, gravel, etc. may selectively deposited within the cells of theprinthead within a container (155 in FIG. 1B) via fill materialdeposition tubes 110. In various embodiments, the data transfer system100 transfers data representing a three-dimensional shape into concretevoxels. During deposition of the fill material and/or extrusion of theconcrete, the cells (e.g., 151) of the printhead 150 may support thevoxel formation of each material within a container. Subsequently, thecontainer (155 in FIG. 1B) supports the outer perimeter of the concretewhile it locks (i.e., cures). With a related function, the fill materialholds the concrete in the correct voxel location within the containerwhile the concrete locks.

FIG. 1B illustrates a cross section of the data transfer system 100 ofFIG. 1A in which voxels 160 of fill material have been deposited andvoxels 160 of concrete have been extruded. The voxels 160 of fillmaterial are shown in dark shading and the voxels 160 of concrete areshown in light shading. A supply component and control system of thedata transfer system 100 is divided into a concrete supply portion 107and a fill material supply portion 106. As the supply portions 106 and107 are extracted upward out of the container 155 along with a printhead150 that may or may not include cells 151 as shown in FIG. 1A. Eachvoxel 160 is ultimately filled with either concrete or a fill material.A controller selectively opens and closes the fill material depositiontubes 110 and the concrete extrusion tubes 120.

FIG. 1C illustrates a perspective view of the data transfer system 100of FIG. 1A for extruding concrete from the concrete supply area 107 anddepositing fill material in from the fill material supply area 106. Athree-dimensional array of voxels 160 are shown with deposited voxels offill material and concrete in dark and light shading, respectively.While the concrete is locking, a container (not shown) may contain thethree-dimensional array of voxels 160. As the printhead 150 havingmultiple cells is retracted out of the container, additional voxels maybe filled with fill material and/or concrete to ultimately form a targetthree-dimensional concrete object or shape.

While the illustrated embodiments contemplate a substantiallyrectangular container, in other embodiments, the container may be anyshape and/or may outline a shape (i.e., have a hollow or unprintedcenter section). For example, the container may approximate a perimeterof a structure having a perimeter thickness corresponding to thethickness of the walls of the structure. Similarly, the examplesprovided herein show an array of eighteen (18) fill material depositiontubes 110 and eighteen (18) concrete extrusion tubes 120 for printing athree-dimensional array of voxels 160 having a length of six voxels, awidth of three voxels, and a height of N voxels, where N corresponds tothe number of voxels printed as the data transfer system 100 isretracted upward.

In other embodiments, each cell of a printhead may include more than oneconcrete extrusion tube 120 and/or more than one fill materialdeposition tube 110. In some embodiments, the printhead may be excludedaltogether and/or the internal cell walls may be excluded. In suchembodiments, the voxels may be form with slightly less definedperimeters if concrete and/or fill material that is extruded ordeposited in one voxel is allowed to flow or spill slightly into aneighboring voxel. Depending on the resolution of the voxels as a wholeand the target exactness of the printed object or shape, such an resultmay not impact the overall result.

FIG. 1D illustrates a bottom view of the data transfer system in FIG. 1Awith selectively openable tubes 110 and 120 for depositing fill materialand extruding concrete, respectively, according to one embodiment. Inthe illustrated embodiment, a controller selectively opens the tubes 110and 120 by moving the tube covers 111 and 121, respectively. In theillustrated embodiment, each cell of the printhead 150 includes one tube110 for selectively depositing fill material and one tube 120 forselectively extruding concrete. In some embodiments, tube covers 111 and121 may be combined as a single unit that has two positions—a firstposition in which concrete is extruded and a second position in whichfill material is deposited. In yet another embodiment, a single valvecontrol unit can be selectively positioned in three positions—a firstposition in which concrete is extruded, a second position in which fillmaterial is deposited, and a third position in which both tubes areclosed.

FIG. 2A illustrates a three-dimensional printing system 200 thatincludes a controller and supply component 210 that feeds aone-dimensional array of injector printheads 230 for injecting a resinhardener 275 into a container 250 of resin 260, according to oneembodiment. As the three-dimensional printing system 200 is slowlyretracted out of the container 250 of resin 260, the controller 210causes the injector printheads 230 to selectively deposit hardener 275.As illustrated, the hardener 275 is deposited as a plurality of voxelsin a target pattern. The illustrated embodiment shows a one-dimensionalarray of seven injector printheads 230. It is appreciated that a largerone-dimensional array and/or a two-dimensional array of injectorprintheads 230 is possible as well.

FIG. 2B illustrates the three-dimensional printing system 200 of FIG.2A, wherein the one-dimensional array of injector printheads 230 isbeing retracted from a container 250 of resin 260 as resin hardener 280is deposited on top of un-locked (i.e., un-hardened) resin hardener 275.Resin hardener 275 and 280 may be injected according to a targetpattern. The resin hardener deposition phase may be completed within afew seconds as the injector printheads 230 are retracted from thecontainer 250 of resin 260. The deposited resin hardener may lock over amuch longer time period as the resin hardens. However, while the firstthree-dimensional object of hardening resin (275 and 280) locks, theprinting system 200 can be used to deposit hardener in one or moreadditional containers of resin—all of which may finish the locking phasein parallel.

FIG. 3A illustrates a three-dimensional printer or printing system 300with a feed 305 for feeding print material into a plurality of injectorprintheads 310. The injector printheads 310 are inserted within an emptycontainer 350. The injector printheads 310 may be very close togetherand may be part of a two-dimensional array of injectors inserted withina three-dimensional container.

FIG. 3B illustrates the cross section of the container 350 with fillmaterial 375 being inserted within the container 350 around theneedle-like injector printheads 310. In various embodiments, theinjector printheads 310 may be inserted into the container 350 after thefill material 375 has been inserted. In other embodiments, the fillmaterial 375 may not easily accommodate the insertion of the injectorprintheads 310 and/or the injector printheads 310 may be too fragile tobe inserted into the fill material 375.

FIG. 3C illustrates the cross section of the container 350 with theneedle injector printheads 310 partially retracted having selectivelyinjected a bonding agent 380 into the fill material 375 at selectivelocations. The bonding agent 380 may be selectively injected to bond thefill material 375 in selective locations to form a bonded,three-dimensional object. The three-dimensional printer 300 may be usedto print successive three-dimensional objects while the fill material375 injected with the boding agent 380 goes through the locking phase.Once the fill material 375 and bonding agent 380 are locked, theun-bonded fill material 375 may be removed to reveal the fully locked,three-dimensionally printed object.

FIG. 4A illustrates a three-dimensional printing system 400 thatincludes a beamforming device 430 for beamforming ultrasound orelectromagnetic radiation to a focus 435 within a fill material 475contained within a container 450. The ultrasound or electromagneticradiation (depending on the embodiment) is focused to cause the fillmaterial 475 to lock at the focus location 435. By moving the focus 435to various locations, a plurality of locked voxels may be formed withinthe fill material 475 corresponding to a three-dimensional object.

FIG. 4B illustrates the focused beam of the beamforming device 430 ofFIG. 4A having hardened five voxels 440 within the fill material 475,according to one embodiment. The three-dimensionally printed voxels 440may be selectively locked at locations to form a two- orthree-dimensional object. In some embodiments, the focus of thebeamforming device 430 may take several seconds or minutes to lock, butthe beamforming device 430 may initiate the hardening (or other lockingprocess) at various voxel locations in succession for parallel locking.

FIG. 4C illustrates the focused beam of the beamforming device 430 ofFIG. 4A having hardened a sequence 437 of voxels to form athree-dimensional object. The three-dimensional object may take severalminutes or hours to fully lock, at which point it can be removed fromthe fill material 475. While the three-dimensional object is locking,the beamforming device 430 may be used to print three-dimensionalobjects in a plurality of other containers filled with a fill material.Each of the printed objects may lock in parallel.

FIG. 5 illustrates a simplified flow chart 500 of a method of printing,according to one embodiment. As illustrated, shape data may be selectedor generated corresponding to a three-dimensional model or system, at502. One or more materials and/or colors may be selected for printing,at 504. A data transfer and locking method is chosen, at 506. Forexample, a resin-based three-dimensional printer with injector needlesmay be used to inject a hardener into resin. As another example, abonding agent may be injected into a fill material, as described above.

In some embodiments, a conventional process may be utilized, at 508, andconventional fabrication, at 514, may be performed. Thethree-dimensional object may be completed, including both a deposition(data transfer) phase and a locking phase, at 516, and the process mayend, at 518. Alternatively, the digital process described herein may beutilized, at 508, in which voxels of print material are producedsurrounded by support material, at 510. All of the print material voxelsare created, at 510, and then the locking process of the various voxelsof print material is performed in parallel, at 512.

FIG. 6 illustrates a flow chart 600 of a specific example of a method ofprinting three objects with parallel locking, according to oneembodiment. As illustrated, shape data is selected or generated from amodel or other system, at 602. One or more materials and/or colors areselected, at 604. A data transfer and/or locking method is chosen, at606. The locking method may be selected based on the inherent lockingparameters of the selected material(s). A three-dimensional printertransfers the data representing a three-dimensional object into aplurality of voxels of print material in a first volume, at 610. Asrepresented by the bold arrow below the box 610, the first printedmaterial may begin a locking phase that takes several minutes, hours, oreven days.

Before the locking phase of the first printed object, 610, is complete(represented by the end of the bold arrow), the three-dimensionalprinter may be used to perform a data transfer of voxels representing athree-dimensional object to a second physical print volume, at 612.While the first and second print volumes 610 and 612 are locking, athird print volume is completed, at 614. Additional print volumes maysubsequently be completed. Ultimately, the print material from the datatransfer stage of the first three print volumes 610, 612, and 614 may becompleted before the first print volume, at 610, has even finishedlocking. Accordingly, the three print volumes 610, 612, and 614 may gothrough the locking phase in parallel.

FIG. 7 illustrates an example of a three-dimensional printing system 700with various modules for controlling the three-dimensional printing,according to one embodiment. The system 700 may include a bus 720 thatconnects a processor 730, memory 740, network interface 750, and acomputer-readable storage medium 770. The computer-readable storagemedium 770 may include one or more modules implemented in hardware,firmware, or software to effectuate the three-dimensional printing withseparated data transfer stages and locking stages.

Specifically, a data transfer module 780 may control the transfer ofdata representing a three-dimensional object into a physical media as aplurality of voxels. A voxel conversion module 782 may convert datarepresenting a smooth-form three-dimensional object into a plurality ofvoxels having a finite resolution for three-dimensional printing. Insome embodiments, a layer generation module 784 may organize the voxelsto be printed as a series of layers. A printhead control module 786 maycause the printheads for depositing a material to be retracted from adeposition surface or container on or within which the three-dimensionalobject is printed as a plurality of voxels. In some embodiments, a fillmaterial control module 788 may control the deposition of a fillmaterial within some voxels to provide support and/or a bondablematerial for supporting or directly becoming the three-dimensionalobject being printed.

This disclosure has been made with reference to various embodiments,including the best mode. However, those skilled in the art willrecognize that changes and modifications may be made to the embodimentswithout departing from the scope of the present disclosure. While theprinciples of this disclosure have been shown in various embodiments,many modifications of structure, arrangements, proportions, elements,materials, and components may be adapted for a specific environmentand/or operating requirements without departing from the principles andscope of this disclosure. These and other changes or modifications areintended to be included within the scope of the present disclosure.

This disclosure is to be regarded in an illustrative rather than arestrictive sense, and all such modifications are intended to beincluded within the scope thereof. Likewise, benefits, other advantages,and solutions to problems have been described above with regard tovarious embodiments. However, benefits, advantages, solutions toproblems, and any element(s) that may cause any benefit, advantage, orsolution to occur or become more pronounced are not to be construed as acritical, required, or essential feature or element. The scope of thepresent invention should, therefore, be understood to encompass at leastthe subsequent claims.

What is claimed is:
 1. A three-dimensional printing system, comprising:a container to selectively receive concrete and fill material; a fillmaterial deposition tube within each of a plurality of cells of aprinthead to selectively deposit fill material within the container; aconcrete extrusion tube within each cell of the printhead to selectivelyextrude concrete within the container; a supply divided into supplycells corresponding to the cells of the printhead, wherein each supplycell is adapted to receive both fill material and concrete, wherein eachsupply cell comprises a first tube cover to cover an opening in the fillmaterial deposition tube when concrete is supplied to the supply cell,and wherein each supply cell comprises a second tube cover to cover anopening in the concrete deposition tube when fill material is suppliedto the supply cell; a retraction assembly to retract the printhead,including the fill material deposition tube and the concrete extrusiontube within each cell of the printhead, from a first depth to a finaldepth within the container; and a controller to: selectively depositfill material in each of a plurality of voxels at various layers withinthe container between the first depth and the final depth, andselectively extrude concrete into each of the plurality of voxels atvarious layers within the container between the first depth and thefinal depth.
 2. The three-dimensional printing system of claim 1,wherein the fill material comprises one of beads, gravel, and sand. 3.The three-dimensional printing system of claim 1, wherein the fillmaterial is deposited in the plurality of voxels corresponding to anoutline of a target three-dimensional object.
 4. The three-dimensionalprinting system of claim 1, wherein each of the fill material depositiontubes has an electronically actuated valve to control the deposition ofthe fill material within the cells of the printhead.
 5. Thethree-dimensional printing system of claim 1, wherein each of theconcrete extrusion tubes has an electronically actuated valve to controlthe extrusion of the concrete.
 6. The three-dimensional printing systemof claim 1, wherein the first tube cover and the second tube cover ofeach supply cell are combined as single unit that has two positions, afirst position in which concrete is extruded and a second position inwhich fill material is deposited.
 7. A three-dimensional printingsystem, comprising: a container to selectively receive concrete and fillmaterial; a fill material deposition tube within each of a plurality ofcells of a printhead to selectively deposit fill material within thecontainer; a first electronically actuated valve to control thedeposition of the fill material within the cells of the printhead; aconcrete extrusion tube within each cell of the printhead to selectivelyextrude concrete within the container; a second electronically actuatedvalve to control the extrusion of the concrete within the cells of theprinthead a supply divided into supply cells corresponding to the cellsof the printhead, wherein each supply cell is adapted to receive bothfill material and concrete, wherein each supply cell comprises a firsttube cover to cover an opening in the fill material deposition tube whenconcrete is supplied to the supply cell, and wherein each supply cellcomprises a second tube cover to cover an opening in the concretedeposition tube when fill material is supplied to the supply cell; aretraction assembly to retract the printhead, including the fillmaterial deposition tube and the concrete extrusion tube within eachcell of the printhead, from a first depth to a final depth within thecontainer; and a controller to: selectively deposit fill material ineach of a plurality of voxels at various layers within the containerbetween the first depth and the final depth, and selectively extrudeconcrete into each of the plurality of voxels at various layers withinthe container between the first depth and the final depth.
 8. Thethree-dimensional printing system of claim 7, wherein the fill materialcomprises one of beads, gravel, and sand.
 9. The three-dimensionalprinting system of claim 7, wherein the first tube cover and the secondtube cover of each supply cell are combined as single unit that has twopositions, a first position in which concrete is extruded and a secondposition in which fill material is deposited.